Gas blast circuit breaker



Aug. 26, 1947. P. l.. TAYLOR 2,426,250

GAS B LAST CIRCUIT BREAKER Filed May 21, 1943 3 Sheets-Sheet l uwnlmnwrP. L. TAYLOR GAS BLAST CIRCUIT BREAKER Aug. 2s, 1947. 2,426,250

Filed' May 21 1943 5 Sheets-Sheet 2 Aug. 26, 1947. P. L. TAYLOR2,426,250

GAS4 BLAST CIRCUIT BREAKER Filed May 21, 1943 3 Sheets-Sheet 3 PatentedAug. 26, 1947 UNITED STATES PATENT OFFICE GAS BLAST CIRCUIT BREAKERApplication May 21, 1943, Serial No. 487,888

9 Claims. l

This invention relates in general to gas blast circuit breakers andparticularly to an improved method of and means for increasing theinterrupting capacity and improving the performance of gas blast circuitbreakers by the control and limitation of the arc products,

In prior art gas blast circuit breakers of the type provided with anozzle or orifice type of contact through which the arc is blasted, theinterrupting ability of the circuit breaker has been considered to beprincipally dependent upon the manipulation of (l) air pressure, (2)Dort area, (3) number of breaks and (4) insertion of resistors. Priorart breakers of this type are limited as to interrupting ability,particularly When built within the space and other limitations of moderncircuit breaker practice. This limitation has been believed by some toresult from the effective plugging of the orifice by an arc core oflarge diameter.

In a particular case, attempts were made to extend the interruptingrange of a prior art gas blast circuit breaker of nozzle contact type toL10,000 amperes at 2300 volts, Within the space and other limitationsdictated by modern circuit breaker practice. It was found that atcurrents of the order of 20,000 amperes and above, the arc was reignitedin or transferred to regions in the circuit breaker Where extinction ofthe arc Was difficult or impossible and the breaker failed. The priorart gas blast circuit breaker of the nozzle contact type was thus foundto be inadequate.

The principal difculty encountered was the failure to adequately controland limit the arc and its products, especially at and before theorifice. it was found that the metallic vapor and particles, developedby the extremely rapid vaporization of the contact material at the pointof contact and arc inception, were driven back along the stream of gas,in a direction adverse to that necessary for efficient interruption.Pressures Were developed of sufficient magnitude to effectively overcomethe pressure of the gas blast in certain sections and to drive the arcproducts back along the gas stream. This caused arc transfer orrestriking of the arc in locations where it Was difficult or impossibleto interrupt the arc. Also, these arc products, after having lost theimpetus imparted to them by the explosive force, are swept back into thezone of the arcing contacts by the gas blast thus prolonging the arcingin that region.

It was further found that the nozzle type of breaker permitted in somecases excessive development or propagation of the arc inception areas,particularly on the stationary contact, in a direction away from theorifice, thereby delaying the movement of the arc terminal to andthrough the orifice and -causing the production of excessive conductingvapor on the gas inlet side of the orifice.

It is therefore an object of the present invention to avoid the abovedisadvantages in a nozzle type gas blast circuit breaker by limiting,controlling and localizing the conductive products of arcing so `as tominimize contamination of the gas blast and to facilitate circuitinterruption.

It is a, further object of the present invention to provide a gas blastcircuit breaker With an interrupting chamber oi geometricalconfiguration such that arc products not immediately scavenged will betrapped and prevented from reaching portions of the interrupter in suchconcentration that their presence is detrimental to the eiicientoperation of the circuit breaker.

It is also an object of the present invention to provide in a gas blastcirc 't breaker, provided with arcing contacts and main current carryingcontacts in circuit therewith, an impediment to the transfer of arcproducts from the region of the arcing contacts to the region of themain current carrying contacts.

It is also an object of the present invention to limit in a gas blastbreaker the development and propagation of the arc inception areas andarc terminals in a direction adverse to that conducive to efficientinterruption and to thereby reduce the time required to drive the arcinto the interrupting zone.

Objects and advantages other than those above set forth will be apparentfrom the following description When read in connection With theaccompanying drawing, in which:

Fig. 1 is a view partly in elevation and partly in cross-section of acircuit breaker embodying the present invention;

Fig. 2 is an axial cross-section through the contact chamber of theembodiment illustrated in Fig. 1;

Figs. 3, 4 and 5 are axial views partly in crosssection of modifiedinterrupting and contact chambers that may be substituted in the circuitbreaker shown in Fig. 1 for the interrupting and contact chambers shownin Fig. 2;

Fig. 6 is a diagrammatic illustration of desirable relative positioningof the main current car- 3 rying contacts and of the arcing contactsshown in Figs. 2, 3, 4 and 5; and

Fig. '.7 illustrates a modified form of the invention as shown in Fig.4.

Elements performing the same function in these different embodiments aredesignated therein by the same reference characters although suchelements may be of'different configuration in the various embodimentsshown.

Referring more particularly to the drawing by characters of reference,reference numeral II designates a reservoir serving both as structuralvelement and as source of supply fluid under pressure for the circuitbreaker. Theiluid utilized may be any of the insulating extinguishing anarc but will be assumed to be compressed air preferably maintainedatf apressure of the order of 100 to 225 pounds per square inch. Reservoir II may be placed in communication with a hollow cylinder I2 dening acontact chamber I3 through a valve I4 and throughl a hollow insulatorI5. The ilow` of iluidfrom reservoir II to. atmosphere continues from`contact chamber i3. through an orifice typecOntact I1 and through an arcextinguishing or interrupting chamber I 8. Chamber lis generally definedby an elbow I9 of conductive material havingasubstantially uniformcross-section and by a` cylinder 23. of insulating material,

Valve I4 is preferably operatedi'by means of `a pneumatic motorZIadapted to be` supplied with air. fromv reservoir II through a valve22. controlled by a solenoid 23. When-valve I4 is open air is alsosuppliedltherethrough to a second air motor 24 serving to open amovabledisconnecting contact 25 cooperating with a xed disconnecting contact21.y Contact 26=may` be reclosed by a third pneumatic motor 28 connectedwith reservoir Il through a valve 2!!` controlled by a solenoid 33. Thecircuit controlled by the circuit breaker is assumed to be analternatingcurrent circuit represented by two sectionsofconductors 3|which are joined to disconnecting contacts-26, 21 inserieswith the mainandfarcing contactsy of the circuit breaker.

As illustrated in Fig. 2, the contact chamberY I3 provided with a pairof relatively movable arcing contacts 5I and52. Contact 5I isillustrated as being stationary and of the type provided withan orificeor nozzle I1: Relatively movable main contacts 32 and33 .are in parallelwith arcing contacts 5I and 52. Contact 32 is preferably made of a`series of segments resiliently mounted, as shown more clearly in Fig. 3,to form an annular stationary contact..

When the main contacts 32, 33 are parted the entire current flowsthrough the arcing contacts 51, 52.- In prior art circuit breakers of'this type, the cooperatingsurfaces of the arcing contacts were ofcopperor some similar material. Asthese contacts were heated by theheavy current flowing therethrough upon opening of main contacts, apoint often near the edge ofv the stationary contact was heated nally toincandescencel The emanationof ionizedparticlesfrom thisincandescent'spot sometimes causedanarc to be struck across the edge ofthe two arcing contacts, even prior to parting thereof.; This'wasconducive to propagation of the arc inception area in a directionadverse to that vnecessaryi'or efficient interruption.

Pressures were` developedin the arc inception region of suhicientvmagnitude to effectively overcome the pressure of the air blast and todrive the conductive particles and vapors back along iluids suitableAfor the air stream. The metallic particles and vapors not onlycontaminated the air stream to be utiized for interrupting the arc, butalso cause arc transfer to or restriking of the arc at the main contactsor in other regions where interruption was difficult or impossible.

In the present invention the metallic vapors and, particlesare localizedandfminimized. As illustrated in Fig.` 2, the contact surfaces 53 and 54are preferably made of a highly arc resistant material such as atungsten-silver sintered mixture effective-to reduce metallic emission.Contact face 54 is made slightly larger in diameter than-contact face53. Insulating material 55, preferably refractory, is providedimmediately adjacent the contact face 54 whereby the root of the-arcforming on the material 54 will be prevented from being driven along thecontact 5I toward the side walls 51.

The arcing contacts 5I and 52 are so shaped and'arranged-as` to expeditethe'propagation of the arc into the orifice I1. The angle at which thecontact faces 53and 54meet issodesigned that'any metal particlesemanating from `the arc region are trapped by. the sidewalls 51 of thechamber I3 and prevented from reaching the main.contacts or otherundesirable'regions. The wall 0r; barrier. member 58 further` isolatesthe mainl contacts 32, 33; from the arcing region of the circuitbreaker.

The operation of the movable' contacts 33 and 'E2-is similar in.a1l themodifications. As illustrated in Fig. 4, the movable main contact 33 isconnected by a spider 1| to astud 4I on which a. piston 42 is secured bypin 43soas to be slidablegin a cylinder 12; Main contact 33 is biasedtogits closed position (shown in Fig. 4) by a spring 44; Arcingcontact52 is threadedonto a hexagonal stud 13 which is slidably mountedsin theinsulating disk 14 and biased to closed position by spring 45; Thestud4I is conductively connected to the stud 13 by means. of` pietails 15.Current entering from theleft handsconductor 3l through connector 16flows through the shell 11, throughmainicontacts 32, 33 and arcingcontacts5l, r52 in-parallel to4 thel stud 4I, disconnect contactsV 2.1,`26 to the-right hand' conductor` 3l. Althoughthe arcingcontacts-.are'closed imparallel.with the mainv contacts, the ow ofcurrent willfgenerally pass almost entirely through the main contactsbecausel ofy they relatively small area of, the cooperating surfaces ofthe arcing contacts and because of the higher resistance thereof.

When the circuitis to be opened, solenoid 23 is energized from asuitablesource of, current (not shown) to cause actuation of valve V22. Thevalve admits compressedair from the reservoir I I to the motor 2l, whichopensthe blast valve I4. Air underpressure-is then supplied from .thereservoir I.I.through,valve I4 to lchamber I 3fand tomotor 2,4. When theair pressure within the contact chamber buildsup substantiallytothepressure of reservoir I I, such pressure is communicated tocylinderA 12 through the aperture 'mthereby moving piston 42` to theright, as. viewed in Fig. 4. against the action of spring 44. Movementof piston42 first separates main contacts 32y 33Iwhile spring 45maintains, arcing contacts 5I, 52. closed. Upon separation of themaincontacts .the flow of current is diverted from the main contacts tothe arcingcontacts. Volatilization of the arcing contact surfaces andemanation of metallic particles therefrom is minimized by the arcresistantcooperating surfaces 53 and 54.

When piston 42 reaches a predetermined position, the insulating disk 'ldengages a shoulder 1S on the stud 'i3 to move contact 52 jointly withcontact 33. Contacts 5l, 5t are thereby separated and an arc is drawntherebetween while a blast of air is projected from the contact chamberi3 into the interrupting chamber lil through orifice The air blastissuing from the contact chamber between contacts 5l and drives the arctoward the interrupting chamber lli. Movement of the root of the arc oncontact in a direction up stream of the blast, is prevented by theinsulatmaterial @Si immediately adjacent the Contact surface rihis arcroot is moved through the orifice l'i to a point on contact 5i near theauzo iiiary contact 8G. The arc is extended and loops into theinterrupting chamber i8 where it ccntacts auxiliary electrode thereuponbreaking into two portions. A. iirst arc portion extends ben tweenelectrodes and and a second portion between electrode and contact 5l orelbow lil.

The rrst arc portion is located in a zone where the air blasting fromthe chamber it at maximum velocity suddenly expands to substantiallyatmospheric pressure w a corresponding drop in temperature. Theincandescent ionized air in the arc path is therefore replaced at arapid rate by cool non-.ionized air, thereby rendering the continuousionization or the arc path possible only as the arc current remains ofrelatively high intensity. rlhis portion of the arc path is shunted byresistor lill, which likewise connects auxiliary electrode with contact52.

When the flow of current through the circuit breaker decreases towardthe end of the first half cycle of arcing, the rate of ionization of thearc path between the electrodes 52 and Sii becomes lower than the rateof deionization of the arc path by the blast. The arc between electrodes52 and 'therefore extinguished, thereby interrupting the fault current.The remnant current thon hows through the circuit breaker through shellll, elbow itl, the remaining second. arc portion, electrode resisto-r Econductor 8i to the disconnect contacts El. 'TL s current is limited toa relatively low value by the resistor Et. The resistance of resistor@il is of relatively high Value so that the current is substantially inphase coincidence with the voltage of the circuit. rllhis currentdissipates the stored energy in the circuit 3 l.

When the voltage reaches zero value, the re` maining arc is easilyextinguished by the air blast, the voltage thereupon reverses andfollows its normal wave without presenting the over-voltages that wouldresult from a current interruption omitting the discharge of the sto-redenergy of the circuit. The air blast carrying the heat dissipated in thearc is cooled and substantially deionized by means of 'cailles S2,

In the embodiment shown in Fig. 3, the Contact chamber i3 is providedwith an insert El@ of insulating material a configuration that willcollect and cool the metallic vapor and particles while at the same timeshielding and isolating the main contacts The inner surface E2 of theinsulating material il@ is arranged to stream line the air flow so as toeffect a sweeping of the zone of arc inception by a high velocityuniform flow of air approaching the orifice l1. The surface ll providesa surface on which metallic particles from the arc may be trapped out ofthe main air stream. The surface 6l may be porous as in the case whereinsert 6l) is of refractory material, and it may be either smooth orribbed.

An illustration of a modiiied combination of throat and trap member isshown in Fig. 7 The ribs l are formed on the insulation @il so that thefaces thereof may easily trap metallic particles, but at the same timeform little impediment to the now of gas. The insulating material lillis preferably refractory although fiber has been found to besatisfactory.

The surface tl is so designed as to form a region of substantiallyreduced velocity or reduced pressure adjacent thereto. This zone ofreduced pressure or reduced velocity is effective in trapping, byeddying or otherwise, metallic vapors emanating from the arc. Thismetallic va por is thereby localized and prevented from reentering themain stream. of air flow in such concentration that its conductingproperties would contaminate the air to utilized for arc extinction.

In the embodiment shown in Fig. Il the insulating material in the arcingchamber i3 is designed to have a greater capacity for trapping andcondensing of metallic vapor and particles although at some sacrifice instreamlining the flow of gas tothe orifice il. The zone of reducedpressure or reduced velocity air in the chamber i3 is more pronouncedthan the interrupting head shown in Fig. 3.

Fig. 5 illustrates another embodiment of the present invention. In thisembodiment the trapping surface li of the insulating material @il ismore closely adjacent the movable arcing contact 52, and therefore thezone of reduced velocity and pressure adjacent the surface il! is lesspronounced.

The markedly improved performance of a circuit lorealier embodyinor thepresent invention over prior art circuit breakers of this type isevidenced by test results on a circuit breaker such as shown in Figs. 3and ll. In one test this circuit breaker performed over 913interruptions on a single set of contacts at currents ranging from10,060 to 40,090 ampercs at 235i@ volts using air pressure at to 1.5i)pounds. On another series of tests, this circuit breaker performed 32interruptions on a single set of contacts at 37,5%@ amperes at 2390Volts using air under pressure of 1GO to ll() pounds. On these series oftests; the visible demonstration was considerably less than in prior artcircuit breakers in current ranges where operative. In the above teststhe fault current was interrupted within one-half cycle after adequateparting of the arcing contacts.

The above tests are particularly good evidence of the improved operationof a circuit breaker embodying the present invention, inasmuch as exceptfor the above disclosed changes in the arcing contacts and contactchamber structure. the circuit breaker tested was the same as the priorart breaker referred to in column l, that failed to interrupt currentsof the order of 20,000 amper-es. The high number of circuitinterruptions possible on a single of contacts is a further measure ofthe improved performance of a circuit breaker embodying the presentinvention.

Fig. 6 illustrates a desirable dimensional arrangement of main andarcing contacts in a circuit breaker of the nozzle contact type. Thedistance a between the liXed main contacts 32 and the fixed arcingcontact lll should be equal i to or greater than twice the distance d,the dis'- tance between they lined arcing contact di and the movablearcing contact when the latter is in the circuit interrupting positionshown in dotted lines.

In the embodiments illustrated in Figs. 2, 3, 4 and 7, the surface isfor at an angle thejet of metallic particles or vapor ejected the aroingcontacts. In 3 4 d 7 angle is substantially a righ-t a -Y near thearcing contacts. ping of the particles and vapor that im such surface.By connecting portion of insulation [lil that is adjacent materi l (andis parallel to the jet of vapor or particles) with the trapping surfacefi! that is substantially at right angles to the jet by a curvedintermediate portion tangential to both, a structure similar to thebucket of a Pelton wheel provided. Any jet of vapor ejected with a highinitial velocity has its velocity reduced by friction and is de` ionizedby the insulating material With the structure shown this trapping isaccomplished with a minimum of cruitamination` of the gas blast. In 7,the surface available for trape ping has been increased by the ribs (l.

Although but several embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that various changes and modications be made therein withoutdeparting from te spirit of the invention or from the scope of uneappended claims.

It is claimed and desired to secure b; Letters Patent:

1. In a gas blast circuit brealer, a Contact chamber, a pair ofrelatively movable arcing con tacts adapted to draw an in said chamber,one of which contacts for?. s orifice providing a gas outlet for saidchamber, a pair of relatively movable main contacts connected in rillclwith saidarcing contacts and arranged so that the distance between themain Contact and the fixed arcing contact is edual to or greater' thantwice the distance between said arcing contacts when in circuitinterrupting position, a gas pas'- sage between said main and arcingcontacts, insulating material lining said and extending from said outletsubstantially to said main contacts, and means for estalilishiiiig aflow ci gas sequentially through and said outlet.

2. In` a gas blast circuit breaker, a contact chamber, a pair ofrelatively movable contacts adapted to draw arc in said chamber, one ofwhich contacts forms an orifice providing a gas outlet for said chamber,means for establishing a flow of gas through said chamber and saidoutlet, and means for trappii f roducts of said arc and providingminimum resistance to said iiow of gas, said means comprising insulatingmaterial surrounding said orifice and provided with ribs formed at anangle to said flow of gas.

3. In a gas blast circuit breaker, a contact chamber, a pair ofrelatively movable arcing contactsthe cooperating faces of which meet ina predetermined surface and are adapted to draw an arc in said chamber,one oi which contacts forms an orifice providing a outlet for saidchamber, means for establishing a flow of gas through said chamber andsaid outlet, and a member of insulating material in said chamberimmediately adjacent orifice and provided with a rst surface portionforming a continuation of said predetermined surface substantially inalignment therewith and provided with a second surface portion forming acontinuation of said first surface portion and extending at asubstantially wide angle therefrom toward one of said contacts.

4. In a gas blast circuit breaker, a contact chamber, a pair oirelatively movable contacts adapted to draw an arc in said chamber, oneof which contacts forms an oriice providing a gas outlet for saidchamber, means for establishing a flow of gas through said cham er andsaid outlet, and means for minimizing mixture of products of arcing withsaid ilow of gas, said minimizing means comprising a, portion of saidchamber providing a region of reduced gas flow adjacent said orificecontact, said minimizing means further comprising a wall of insulatingmaterial in said chamber forming a continuation of the arcing surface ofsaid orice contact.

5. In a gas blast circuit breaker, a contact chamber, a pair ofrelatively movable contacts adapted to draw an arc in said chamber, oneof which contacts forms an orifice providing a gas outlet for saidchamber, means for establishing a flow of gas through said chamber andsaid outlet, and means for minimizing mixture of products of arcing withsaid .flow of gas, said minimizing means comprising a portion of saidchamber providing,r a region of reduced pressure adjacent said orificecontact, said minimizing means further comprising a wall of insulatingmaterial in said chamber forming a continuation of the arcing surface ofsaid orifice contact.

6. In a gas blast circuit breaker. a contact chamber, a pair ofrelatively movable arcing contacts provided with coacting surfacesadapted to draw an arc therebetween in said chamber, one of which arcingcontacts iorms an orice providing a gas outlet for said chamber, a pairof main current carrying contacts connected in parallel with said pairof arcing contacts, means for establishing a flow or gas through saidchamber and said outlet sequentially across said main contacts and saidarcing contacts, means i comprising a surface of insulating materialforming a continuation of said coacting surfaces and extending in saidcontact chamber at a substantial angle to a plane through said coactingsurfaces to a position substantially between said pair of main contactsand said pair of arcing contacts for trapping products of arcing at saidarcing contacts and minimizing mixture of said products with said gasflow.

7. A gas blast circuit breaker comprising a contact chamber' forming aportion of a passageway for gas flow, an interrupting chamber forminganother portion of said passageway, said another passageway portionhaving a cross-sectional area greater than the cross-sectional area oisaid pas-- sageway portion in said contact chamber whereby said gas mayexpand upon entering said interrupting chamber from said contactchamber, a pair of relatively movable contacts, one of said contactsbeing an orifice type contact constitu*- ing a third portion of saidpassageway and connecting said chambers, the other of said contactsbeing adapted to draw an arc substantially at the Contact chamber end ofsaid orifice contact, means for establishing a flow of gas through saidpassageway for moving a portion of arc into said interrupting chamber,means preventing movement of the root of said arc on said orifice typeContact in adirection away from said interrupting chamber, said movementpreventing means comprising an insulating surface in said contactchamber forming a continuatio-n of the arc drawing surface ci saidorifice contact, and said movement preventing means further comprisingdiiicultly vaporizable material on the arcing surface of said orificeContact immediately adjacent said insulating material and on thecooperating contact surface of said other arcing contact.

8. In a gas blast circuit breaker, a first charnber provided with a pairof main contacts therein, a second chamber provided with a pair ofarcing contacts therein connected electrically in parallel with saidmain contacts, an interrupting chamber adjacent said second chamber,means for establishing a flow of gas sequentialy through said first,second and interrupting chambers, and means comprising a barrier memberpositioned between said pair of arcing contacts and said pair of maincontacts for impeding movement to said pair of main contacts of productsof arcing emanating from an arc at said pair of arcing contacts.

9. In a gas blast circuit breaker, a rst chamber provided with a pair ofmain contacts therein, a second chamber provided with a pair of arcingcontacts therein connected electrically in parallel with said maincontacts, an interrupting chamber adjacent said second chamber, meansfor establishing a flow of gas sequentially through 10 said first,Second and interrupting chambers, and means comprising a barrier memberof insulating material positioned between said pair of arcing contactsand said pair of main contacts for impeding movement to said pair ofmain contacts of products of arcing emanating from an arc at said pairof arcing contacts.

PHILIP L. TAYLOR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,287,039 Jansson June 23, 19422,125,525 Thommen Aug. 2, 1938 1,928,470 Whitney et al Sept. 26, 19332,282,268 Thommen May 5, 1942 1,955,213 Whitney et al. Apr. 1'1, 19342,106,032 Lange Jan. 18, 1938 2,063,173 Lange Dec. 8, 1936 1,532,081Rankin Mar. 31, 1925 FOREIGN PATENTS Number Country Date 352,826 GreatBritain July 16, 1931

